1. Technical Field
The present invention relates to a polymerizable monomer feed composition and methods for the polymerization thereof. More particularly, the invention pertains to the economical manufacture of dicyclopentadiene which has a high polymerization activity suitable for reaction injection molding in the presence of a metathesis catalyst.
2. State of the Art
Cycloolefins have been in-mold bulk polymerized via metathesis ring-opening polymerization to obtain molded articles having desirable physical properties. The polymerization reaction is catalyzed by a two part metathesis catalyst system. One part contains a tungsten or molybdenum catalyst and the other part contains an organoaluminum cocatalyst.
A reaction injection molding (RIM) process has been commercially employed to obtain in-mold polymerized articles. RIM involves mixing at least two low viscosity reactive monomer streams and injecting the combined streams into a mold where the monomer quickly polymerizes into a solid polymeric article of a desired configuration. One of the monomer streams contains the catalyst component, while the other monomer stream contains the cocatalyst component.
Dicyclopentadiene (DCPD) can be polymerized in such a manner resulting in a product with very desirable physical properties. A problem that has been encountered in carrying out such polymerization reactions is that contaminates and impurities present in commercially available DCPD monomer inhibit the polymerization reaction by inhibiting the metathesis catalyst system. Commercially available DCPD monomer has a purity of about 95%, and satisfactory molded products cannot be obtained from such DCPD. Accordingly commercially available DCPD must be purified in order to prevent impurities from inhibiting the polymerization reaction.
Many purification methods have been suggested, such as treating DCPD with molecular sieves, alumina, or silica as disclosed in U.S. Pat. No. 4,584,425. Contacting DCPD with an alkaline compound, or heat treating DCPD have been disclosed in Japanese Kokai applications HEI 1-96140 and SHO 63-234017, respectively. However, these methods do not improve the degree of polymerization sufficiently. Even a highly purified DCPD monomer that contains a small amount of polymerization inhibiting components lead to reduced polymerization activity and an unstable polymerization reaction. Hence, a simple and effective method for deactivating such polymerization inhibiting components is needed.